A claw pole type motor is a motor including a stator in which a plurality of claw poles extending in the axial line direction of a rotary shaft are arranged along the circumference, and a rotor in which a plurality of permanent magnets are arranged along the circumference, wherein the motor rotates the rotor using an attractive force and a repulsive force generated between the claw poles and the permanent magnets by changing the polarities of the claw poles. A representative claw pole type motor is disclosed in Patent Document 1.
The stator includes a U-phase core including a U-phase core main body in which a plurality of U-phase claw poles(ok?) are arranged at equidistant intervals along the circumference, a V-phase core including a V-phase core main body in which a plurality of V-phase claw poles are arranged at equidistant intervals along the circumference, a W-phase core including a W-phase core main body in which a plurality of W-phase claw poles are arranged at equidistant intervals along the circumference, a U-phase coil to magnetize the U-phase claw poles, a V-phase coil to magnetize the V-phase claw poles, and a W-phase coil to magnetize the W-phase claw poles.
The U-phase core main body includes a first elongation portion extending toward the W-phase core, the V-phase core main body includes a second elongation portion extending toward the U-phase core and the W-phase core, and the W-phase core main body includes a third elongation portion extending toward the U-phase core. The V-phase core is positioned between the U-phase core and the W-phase core, and the V-phase core, the U-phase core, and the W-phase core are arranged in the axial line direction of the rotary shaft.
In the motor configured as described above, a UV gap may be made between the fore-end surface of the first elongation portion and the fore-end surface of the second elongation portion extending toward the U-phase core, due to fabrication errors. Also, a VW gap may be made between the fore-end surface of the second elongation portion extending toward the W-phase core and the fore-end surface of the third elongation portion, due to fabrication errors. It is preferable that the first elongation portion contacts the second elongation portion, and the second elongation portion contacts the third elongation portion, however, in many cases, gaps are made between the first elongation portion and the second elongation portion and between the second elongation portion and the third elongation portion, due to fabrication errors and assembly tolerances.
If a magnetic flux is generated by current flowing through the U-phase coil, the V-phase coil, or the W-phase coil, the magnetic flux passes through the U-phase core main body, the V-phase core main body, and the W-phase core main body to magnetize the U-phase claw poles, the V-phase claw poles, and the W-phase claw poles. At this time, the magnetic flux passing between the U-phase core main body and the V-phase core main body, and the magnetic flux passing between the V-phase core main body and the W-phase core rain body pass between the first elongation portion and the second elongation portion or between the second elongation portion and the third elongation portion. Accordingly, the magnetic flux passes through any one of the UV gap and the VW gap.
The magnetic flux passing between the U-phase core main body and the W-phase core main body passes between the first elongation portion and the second elongation portion and between the second elongation portion and the third elongation portion, since the V-phase core is positioned between the U-phase core main body and the W-phase core main body. Accordingly, the magnetic flux passes through both the UV gap and the VW gap.
However, since air gaps are formed in the UV gap and the VW gap, and the permeability of air is greatly different from the permeability of iron forming the cores, the UV gap and the VW gap act as magnetic resistance.
Accordingly, the magnetic resistance of the magnetic flux passing through both the UV gap and the VW gap becomes greater than that of the magnetic flux passing through any one of the UV gap and the VW gap, and accordingly, a total amount of magnetic flux decreases so that distortion occurs in the amount of magnetic flux for magnetizing the claw poles. As such, if distortion occurs in the amount of magnetic flux, the rotation of the motor is interfered, resulting in vibration or noise of the motor.
If the motor is configured with the U-phase core, the V-phase core, and the W-phase core, first space is formed between the U-phase core main body and the V-phase core main body, and second space is formed between the V-phase core main body and the W-phase core main body. The U-phase coil, the V-phase coil, and the W-phase coil are disposed in the space formed in the insides of the cores, and the V-phase coil is divided into two V-phase coil elements connected in series to each other.
In this state, the U-phase coil and one of the V-phase coil elements are disposed in the first space, and the other one of the V-phase coil elements and the W-phase coil are disposed in the second space. In this case, since the coils can be disposed in the insides of the cores, the motor can be miniaturized.
In the motor configured as described above, a supply voltage is applied to the individual coils to make current flow through the coils and generate magnetic fluxes around the coils, so that the magnetic fluxes pass through the individual core main bodies to magnetize the claw poles. If the winding directions of the coils are different, the magnetic fluxes are generated in different directions, so that the polarities of the claw poles change. Accordingly, by differentiating the winding directions of the U-phase coil, the V-phase coil, and the W-phase coil, and sequentially change the coil to which the supply voltage is applied, the polarities of the claw poles can change appropriately.
Amounts of magnetic flux to magnetize the claw poles of the U-phase core and the W-phase core may be the same as amounts of magnetic flux generated in the U-phase coil and the W-phase coil, respectively.
Meanwhile, an amount of magnetic flux to magnetize the claw poles of the V-phase core may be a sum of amounts of magnetic flux generated in the V-phase coil elements, however, a magnetic flux generated in each V-phase coil element is divided into a magnetic flux toward the claw poles of the V-phase core and a magnetic flux toward the claw poles of the U-phase core or the W-phase core. Accordingly, an amount of magnetic flux toward the claw poles of the V-phase core from each V-phase coil element may be half the generated amount of magnetic flux.
Accordingly, in order to equalize the amounts of magnetic flux to magnetize the claw poles of the U-phase core, the V-phase core, and the W-phase core, an amount of magnetic flux that is generated in each V-phase core element may need to be adjusted to an amount of magnetic flux that is generated in the U-phase coil or the W-phase coil. Accordingly, the U-phase coil, each V-phase coil element, and the W-phase coil may need to have the same number of windings.
However, if the U-phase coil, the W-phase coil, and each V-phase coil element have the same number of windings, the U-phase coil, the W-phase coil, and the V-phase coil element may have the same resistance value. Since the resistance value of the V-phase coil is a sum of the resistance values of the two V-phase coil elements, the resistance value of the V-phase coil may become greater than the resistance value of the U-phase coil or the W-phase coil. As such, if the resistance values of the U-phase coil the V-phase coil and the W-phase coil are different from each other, current flowing through the individual cores may be unbalanced so that the rotation of the motor becomes unstable, resulting in the generation of vibration or noise.
In another claw pole type motor disclosed in Patent Document 2, the number S of the U-phase claw poles, V-phase claw poles, and W-phase claw poles is 12, and the number P of the N poles and S poles of the rotor is 8. Accordingly, the relation of S:P is 3:2, and in the proportional relation, the N poles and S poles of the rotor correspond to the U-phase claw poles, V-phase claw poles, and W-phase claw poles of the stator.
The relation will be understood with reference to FIG. 13. Referring to FIG. 13, when an electrical angle is represented by a circumferential angle, the circumferential angle of each of the N pole and the S pole becomes 180 degrees, and a circumferential angle obtained by summing the circumferential angles of the U-phase claw pole, the V-phase claw pole, and the W-phase claw pole corresponds to the circumferential angle of 360 degrees obtained by summing the circumferential angles of the N pole and the S pole. Accordingly, the maximum circumferential angle of each claw pole becomes 120 degrees.
However, the motor disclosed in Patent Document 2 has a problem that it cannot reduce cogging torque and the distortion of magnetic flux interlinkage. In order to resolve the problem, the circumferential angle of each claw pole needs to be within a range of 130 degrees to 160 degrees, however, in the motor disclosed in Patent Document 2, since the maximum circumferential angle of each claw pole is 120 degrees, the motor cannot reduce the distortion of magnetic flux interlinkage.
In addition, the U-phase core, the V-phase core, and the W-phase core are molded by pressing a magnetic material in a powder state in the axial line direction of the rotary shaft, errors are generated in accuracy of dimension in the axial line direction of the rotary shaft, so that air gaps may be formed between the U-phase core main body and the V-phase core main body and between the V-phase core main body and the W-phase core main body.
In this case, since the permeability of air is greatly different from that of the magnetic material configuring the cores, air acts as magnetic resistance, and the magnetic resistance generates deviation in the amount of magnetic flux passing through each core. Accordingly, the deviation in the amount of magnetic flux may influence the performance of the motor.
Also, Patent Document 3 discloses a motor manufactured by dividing a stator into a plurality of parts, fabricating each part through press processing, and then assembling the parts.
If a motor is manufactured by dividing a stator into a plurality of parts, the mass density of each part increases, which leads to an increase in mass density of the entire stator. Also, it is difficult to align the center axes of the plurality of parts divided in the diameter direction upon assembly. If the center axes of the plurality of parts are dislocated, the roundness of the claw poles deteriorates so that the rotation of the motor may be distorted, resulting in vibration or noise of the motor.
The above descriptions, Patent Document 1 is Japanese Patent Laid-open Publication No 2007-116847, Patent Document 2 is Japanese Patent Laid-open Publication No. 2005-180285, and Patent Document 3 is Japanese Patent Laid-open Publication No. 2008-079384.